Carburetor



July 28, 1936. L D BOYCE 2,048,727

CARBURETOR Filed Feb. 20, 1932 2 Sheets-Sheet l @Tra RNAi-r July 2s,1936.

L. D. BOYCE CARBURETOR Filed Feb. 20, 1952. 2 Sheets-Sheet 2 IN1/FN Torea .o M e M 0 t Patented July 28, 1936 UNITED STATES PATENT OFFICECARBURETOR Application February 20,1932, serial No. 594,337

8 Claims.

This invention relates to carburetors for internal combustion engines.In carburetors of this type, some difliculties are encountered inproducing a mixture of correct proportions for low speed operation andstill providing suiilcient capacity for extreme high speed operation.The plain tube carburetor is usually provided with one or more venturisor stream lined restrictions in the air passageway for the purpose ofincreasing the l0 velocity of the air at one point only without undulyincreasing the total resistance to the flow of air through thecarburetor. The mixing of fuel with the main body of air is usually doneat the throat of these venturis or just posterior thereto.

In order to produce suicient velocity in the air stream at the throat ofthe venturi to draw fuel from the nomle in suilicient quantities and tovaporize such fuel under low speed conditions, it is desirable to have acomparatively small venturi,

so that the velocity of the air stream at its throat will be high. Onthe other hand, a small venturi presents such a resistance to the iiowof air that it will not pass suilicient air to operate the engine at itsmaximum power and speed. It is accordingly customary to make a sort ofcompromise between small and large venturi sizes so as to get fairlygood low speed efficiency and fairly good high speed operation, butwithout obtaining ideal conditions at either end.

Another difliculty encountered in carbureting modern internal combustionengines is due to changing temperatures. With the throttle in closedposition, the high vacuum existing in the intake manifold lowers theboiling point of the fuel and vaporizes the greater part of it. When thethrottle is opened suddenly, the pressure is increased to somethingapproaching normal atmospheric pressure. This increase of pressureraises the boiling point of the gasoline in the manifold and causes someof it to condense and settle on the walls of the manifold, leaving theair with comparatively little fuel in it to be admitted to the engine.

It is accordingly customary to provide an accelerating well oraccelerating pump to supply an additional charge of fuel during theopening vmovement of the throttle so as to wet the manifold. Naturally,the amount of fuel which condenses in the manifold is dependent to agreat extent on the temperature, and it is impossible to work out aquantity for the pump discharge which will be suicient to wet themanifold when it is cold without having too much for satisfactoryoperation when the temperature is high.

It is an object of this invention to produce a (ci. zel-s4) carburetorin which the size of the venturis may be made large enough to supplymaximum quantities of fuel mixture and to provide means for supplyingsuiiicient fuel to the carburetor under low speed conditions. 5

It is a further object of this invention to provide a carburetor havingmeans for automatically regulating the amount of fuel supply for wettingthe manifold in accordance with the temperature.

-Other objects of the invention will appear from 10 the followingdescription and accompanying drawings, referred to which:

' Figure 1 shows a side elevation of a carburetor constructed inaccordance with this invention, with parts broken away for betterillustration of 15 others.

Figure 2 is a view partly in section taken along the line 2-2 of Figure1.

Figure 3 is a view partly in section showing a modified form of myinvention. 20

Figure 4 is a sectional view showing a modi cation of the piston anddash pot.

Figure 5 is a supplementary sectional view taken along the line 5-5 ofFigure 4.

Referring to the device shown in Figures 1 and 25 2, the referencenumeral I indicates the body of the carburetor. This body is providedwith a flange 2 for attachment to the intake manifold of an internalcombustion engine. An air horn 3 is either open to the atmosphere orconnected to an 30 air cleaner or silencer. It will be understood thatair enters through the air horn 3 and passes through the comparativelylarge air chamber 4 from which it enters the venturi 5 and passes on upthrough the mixing chamber 6, past the 35 throttle l and into the intakemanifold 8. The fuel is supplied either by gravity or any other suitablesource of pressure.

In Figure 2, I have diagrammatically indicated a pump 9 which receivesthe fuel from any source 40 and delivers it through a pipe l0 to theinlet fitting Il of the carburetor. 'I'he carburetor is provided with asupply bowl I2, and the fuel is maintained at a substantially constantlevel A-A in the bowl by a oat I3 pivted at Il to operate. 45 the floatvalve I5. This structure is conventional and will be clearly understoodby those skilled in the art.

The carburetor body is provided with an extension I6 having a fuel inletI1 below the fuel level 50 'in the bowl, and the fuel ows up through anozzle or standpipe I8 which discharges at the throat of the venturi 5.The fuel may be premixed with air to any desired extent by air bleedingor by one or more primary venturis, but it is 55 eventually dischargedeither in the form of liquid spray or emulsion at the top of the nozzleI8.

It will be understood that the usual idling tube may be pr'ovided ifdesired, but the construction of this is Well known and has no relationto the present invention. It may be noted, however, that the adjustingscrew 9 controls the richness of the idle mixture.

The throttle 1 is carried by a shaft 20 which may be operated by anysuitable means, such as the operating arm 2|. A crank 22 is attached tothe throttle shaft, and a link 23 is pivoted to the outer end'of thecrank. A pump cylinder 24 is mounted in any suitable manner inside oroutside of the bore l2, and an inlet check Valve 25 for the pump isarranged to communicate with the fuel in the bowl. A passageway 26provides communication between the inlet check valve and the lower partof the pump cylinder 24. An outlet nozzle 21 is also provided fordischarging fuel from the pump into the air chamber or venturi, and anoutlet check Valve 28 is provided to prevent the admission of air to thepump through the nozzle 21. The cylinder 24 is provided with the piston29 having a suitable packing leather 30 and a return spring 3|. A smallcoil spring 32 is provided for holding the packing leather in place, anda retainer 33 forms a seat for the spring 3| and also prevents thedisplacement of the packing leather and spring 32.

A chamber 34 is formed in the piston. 'I'hs chamber is substantiallyfilled with oil or some uid having a marked change in viscosity withchanges in temperature. A dash pot piston 35 is slidably mounted in thechamber or cylinder 34, and this dash pot piston is carried by a rod 36slidably mounted in the cap 31 of the chamber or dash pot 34. A suitablepacking washer 38 is mounted in the top of the dash pot to prevent theloss of oil therefrom. 'Ihe rod 36 is provided with a grooved guideportion 39 serving as a guide for its lower end, a suitable recess orbore being formed in the bottom of the dash pot for that purpose. ltwill be understood that the connectling rod or link 23 is suitablypivoted to the upper end of the rod 36, as at 40.

The operation of the device shown in Figures 1 and 2 is as follows:

Fuel being supplied to the bowl l2 and suction being applied to thecarburetor by the engine,

the fuel iiows through the' nozzle |8 and is mixed with vthe main bodyof air in the mixing chamber 6. When the throttle valve is closed, verylittle fuel will be discharged from the nozzle I8 and perhaps none atall, but it will be understood that the supply under these conditions istaken from the idle tube in a conventional manner. As the throttle valveis opened, the dash pot piston 35 starts to move downwardly through theoil filled dash pot, but due to the resistance of the oil flowing aroundthe dash pot piston 35, the piston 29 will be forced downwardly in vthemeasure in which the oil resists the movement of the dash pot piston. Itwill be understood that the viscosity of the oil is dependent on thetemperature, and accordingly with less temperature, the oil will bestier and more viscous and a greater movement of the piston will result.The fuel discharged from the cylinder 24 by the piston 29 will besprayed into the air chamber of the ca rburetor in the usual manner, andthe spray may be directed into the venturi or any other desired part ofthe carburetor. It will be understood that when the temperature isextremely high, the oil in the dash pot 34 would be so thin that verylittle movement of the piston 29 will result, but when the temperatureis low, the oil will become so stiff that a full stroke of the piston 29will be given at each full opening movement of the throttle. 5

It may be noted that practically any desired range of operation may beobtained by Calibrating the clearance of the piston 35 in the dash pot,and coordinating this with the quality of oil used in the dash pot andin connection with this, it may be stated that the viscosity ranges ofvarious oils are well known, and, if desired, suitable quantities of waxor glycerine or castor oil may be mixed with the mineral oil or otherfluid used in the dash pot for procuring the desiredviscositytemperature curve.

With reference to the device shown in Figure 3, the pump cylinder' 4| ismounted on the body of the carburetor and is provided with an outletpassageway 42 communicating with a passage 43 in 20 the body of thecarburetor which, in turn, has a discharge outlet in the nozzle 44. Anoutlet check valve 45 to prevent the admission of air at the nozzle maybe provided, if desired, but it is not absolutely necessary, because thenormal tend- 25 ency of the fuel is to ow in the other direction. Thefuel is admitted to the carburetor through the tting 46 from any sourceof supply under pressure, such as the engine driven pump 41. It shouldbe understood, however, that any pressure 30 means may be used, such asa gravity tank, and in certain instances I prefer to use comparativelyhigh pressures, so that the fuel issuing from the nozzle 44 will bebroken up into ne particles.

A conduit 48 leads from the tting 46 to the lower end of the pumpcylinder and, if desired, a check valve 49 may be located in theconduit. Instead of connecting the conduit 48 to the tting 46, I mayconnect it to the float chamber l 2 below the fuel level, so that theadditional fuel will be supplied by suction and manual pressure insteadof by pressure of pump 41. A valve 50 is attached to the piston 5| bymeans ofthe bowl and gasket joint-52, and a suitable return spring 53 isprovided to normally hold the piston 5| in its uppermost position. Adash pot 54 fitted with the piston 55 is formed in the upper part of thepiston 5|. The walls of the dash pot are smaller than the cylinder 4|,thereby forming an annulus 56 surrounding the dash pot. A check valve 51controls the by-pass 58 leading from the annulus to the dash pot, and acalibrated passage 59 is provided to permit restricted flow of fluidfrom the dash pot into the annulus. A suitable cap 60 is provided forthe top of the dash pot, and a cover 6| for the top of the cylinder.

It will be understood that the piston 5| may serve merely as a guide, inwhich case it would be made of considerably smallerv diameter than thecylinder 4|, say from ten to fifteen thousandths of an inch, or it maybemade a substantial flt so that the displacement of the piston will, initself, discharge fuel through the nozzle 44.

It will also be understood that the piston 5| may be completely sealedagainst leakage of gasoline, so that the upper chamber or dash pot maybe filled with a heavy oil. This sealing might be accomplished in anyone of several ways: For instance, the piston may be constructed asshown in Figures 4 and 5 in which the piston 62 carries an inner shell63 correspending to the shell 54, as shown in Figure 3. An outer shell64 is also formed on the piston so that the annular space 65 iscompletely enclosed. 75

The top of the inner and outer shells is sealed by a cover E6, and, ifdesired, packing may be applied to the stem of the piston 55. Ifdesired, a packing leather might be applied to the piston 62 to furtherresist the mixing of the fuel with the fluid in the dash pot. It willalso be readily understood that connections or conduits may be providedto permit uld to be conveniently supplied to the dash pot. These are notshown, as their provision would be obvious to any mechanic.

'I'he operation of the device is as follows:

Starting with the parts in the position shown in Figure 3, the throttlebeing in closed position, substantially no fuel is drawn from the nozzleI8 and none from the nozzle I4, but when the throttle is opened, thepiston 55 moving in the dash pot 54 carries.with it the piston 5I andthereby opens the valve 50. This permits an additional supply of fuel toow through the valves 49 and 50, the pistons 42 and 43, and the nozzle44 into the mixing chamber. When the throttle is held in wide openposition, the piston 55 contacts with the valve 5l in such a manner asto hold the piston 5l down against the spring 53, thereby holding thevalve 50 continuously in open position. In this manner, a continuousconstant charge of fuel is provided in addition to the fuel that may bedrawn from the nozzle i8. At low speeds of the engine, for instance, upto 400 R. P. M. with the throttle in wide open position, this issubstantially the only fuel supply to the carburetor, but the size ofvthe nozzle d may be so calibrated with respect to the pump pressure asto give a proper fuel mixture ratio at these speeds, and the shape ofthe curve may be further improved by employing a pump (l) which iscapable of giving a pressure which varies in accordance with the speed.

By the provision of the constant low speed supply, the necessityforrestricting the throat of the venturi 5A is obviated, for the mainnozzle does not have to supply fuel at low speeds and wide openthrottle. It will be understood that the part throttle operation istaken care of by the idle tube, which may be of conventionalconstruction.

It will be understood that by the use of the check valve 49, priming ofthe carburetor may be accomplished the same as with any ordinaryaccelerating pump. That is to say, the operator, by opening the throttlevalve, can discharge a stream of fuel through the nozzle 44 prior tostarting the engine.

I claim:

1. In a carburetor, means forming a mixing conduit, a throttle valve forcontrolling the ow of fuel mixture through said conduit, a pumpconnected with said throttle for discharging fuel into said mixingconduit when said throttle is opened, said pump having a piston, a dashpot connection between said piston and said throttle, and a viscousfluid in said dash pot, the viscosity of said uid varying withvariations in temperature, whereby the stroke of said piston will beautomatically varied according to the temperature, a second pump forsupplying fuel to said rst named pump, and a valve operated inconjunction with the throttle to permit iiow of fuel from said lastnamed pump thru the first named pump to the mixing conduit when thethrottle is in a predetermined position.

2. In a carburetor, means forming a mixing conduit, a main Venturi insaid conduit, a fuel bowl, a nozzle receiving fuel from said fuel mainventuri, a throttle valve for controlling the flow of mixture from saidcarburetor, a fuel pump operated by said throttle valve to dischargesupplementary fuel to said mixing conduit upon opening movements of thevalve, said pump having a piston, a dash pot forming a connectionbetween said piston and said throttle, said dash pot being filled with auid having a marked change in viscosity under changes in temperature, asecond pump for supplying fuel to said first named pump, valve meansnormally preventing the flow of fuel from the last named pump to thefirst named pump, and means for holding said valve in open position whenthe throttle is in open position.

3. An accelerating pump for carburetors comprising a piston, a dash potin said piston, a cover for said dash pot, a piston for said dash pothaving a piston rod extending through said cover, and a packingdevicefor said piston rod held in place by said cover.

4. In a carburetor, means forming a mixing conduit, means forming aconstant level supply chamber, means for supplying fuel under pressureto said carburetor, a main nozzle operated by suction to convey fuelfrom said constant level supply chamber to said mixing conduit, athrottle for controlling the discharge of mixture from said carburetor,a pump operated by said throttle for discharging additional fuel intosaid carburetor when said throttle is opened, and a valve operated bysaid throttle for admitting fuel direct from said source of pressureinto said mixing conduit.

5. In a carburetor, means forming a mixing conduit, means forming aconstant level supply chamber, a nozzle operated by suction to withdrawfuel from said constant level supply chamber and discharge it into saidmixing conduit, means for supplying fuel to said carburetor underpressure, a float controlled valve for maintaining the fuel at aconstant level in said chamber, a by-pass for supplying fuel to saidmixing conduit direct from said source of pressure without passingthrough said constant level chamber, a manually operable throttle valve,a valve controlling said by-pass, and connections holding said by-passvalve in open position whenever said throttle is moved beyond apredetermined point in its opening movement.

6. In a carburetor, means forming a mixing conduit, means forming aconstant level supply chamber, a nozzle operated by suction to withdrawfuel from said constant level supply chamberI and discharge it into saidmixing conduit, means for supplying fuel to said carburetor underpressure, a float controlled valve for maintaining the fuel at aconstant level in said chamber, a by-pass for supplying fuel to saidmixing conduit direct from said source of pressure without passingthrough said constant level chamber,

a throttle for controlling the iiow of mixture from said carburetor, anda valve operated by said throttle for controlling the ow of fuel throughsaid by-pass, said valve being opened temporarily and then closed uponpartial opening movements of the throttle, and being held open when andas long as said throttle is in fully open position.

'7. In a carburetor, means forming a mixing conduit, a throttle forcontrolling'the flow of fuel through said conduit, a. source of suctionbowl and discharging near the throat of said for drawing mixture throughsaid carburetor lncluding an intake manifold, a source of pressure forsupplying fuel to said carburetor, suction operated means for supplyingfuel to said mixing conduit, a supplemental fuel supply means foradmitting fuel to said carburetor directly from said source of pressure,said supplemental fuel supply means being temporarily operated bypartial opening movements of the throttle and being continuouslyoperated when said throttle is held in fully open position. A

8. In a carburetor, means forming a mixing conduit, a throttle forcontrolling the iow of fuel through said conduit, a. source of suctionfor drawing mixture through said carburetor including an intakemanifold, a source of pressure for supplying fuel to said carburetor,suction operated means for supplying fuel to said mixing conduit, asupplemental fuel supply means for admitting fuel to said carburetordirectly from said source of pressure, said supplemental fuel supplymeans being at least temporarily operated by any opening movement of thethrottle, and said supplemental supply means being maintained inoperation at least as long as said throttle is held in fully openposition.

LEONARD D. BOYCE.

